The conventional metal materials have good toughness and strength at low temperatures. However, at high temperatures, these materials have low strength and corrosion-resistance. The intermetallic materials have properties between those of metallic and ceramic materials. The intermetallic materials have lighter high-temperature strength than metal, and are not easily cracked as ceramics. Components in certain applications such as aerospace engines and gas turbines are normally operated at high-temperature surroundings. One end (or one side) of each of these components must have intermetallic characteristics such as the good strength at high temperatures and oxidation-resistance. The other end (or the other side) has metallic properties, i.e., it is tough and ductile at low temperatures. For example, components for constructing the starting motor of a national aerospace plane must be light and good in mechanical strength. Furthermore, the combustion-contact portion of the component must be high-temperature-resistant, oxidation-resistant, and corrosion-resistant. The conventional materials cannot meet all the requirements. However, a functionally gradient material (FGM) can solve the above-mentioned problems. The functionally gradient material can be made through combustion synthesis. In combustion synthesis, the reactants are made into a compact and then the compact is combusted to form the product. Conventionally, the composition ratio of the reactants in the compact is gradient-distributed or the compact is formed by several layers with different values of composition ratio so that the composition ratio of the whole compact is stepwise distributed. Then, the compact is combusted and compressed to be dense. The procedure for preparing a compact with gradient-distributed (or stepwise distributed) composition is very complex. Besides, the gradient of the material properties is determined when the compact is prepared. That is, when different functionally gradient materials are needed, different compacts must be prepared. Accordingly, the manufacturing time and cost are increased.
It is then attempted by the present invention to solve the above-mentioned problems.